How do you trigger a Lambda function - name several event sources.
AWS · Intermediate level
Answer
Lambda can be triggered by API Gateway, ALB, S3, SQS, SNS, EventBridge, DynamoDB Streams, Kinesis, Step Functions, CloudWatch Logs, Cognito, and direct SDK calls. The trigger determines retry, batching, and failure behavior.
Technical explanation
Each event source has different retry, batching, ordering, and failure semantics; idempotency is mandatory.
Serverless design shifts server operations to AWS but increases the importance of event semantics, timeouts, retries, idempotency, concurrency, and downstream protection.
Observability must include structured logs, metrics, traces, DLQs or failure destinations, and alarms on errors, throttles, duration, and age/lag where applicable.
Cold starts, package size, runtime choice, and VPC dependencies should be measured against p95/p99 latency rather than assumed.
Hands-on example
1. Build a small event-driven flow using Lambda plus the relevant event source such as API Gateway, S3, SQS, or EventBridge.
2. Configure timeout, memory, reserved concurrency, IAM role, structured logs, metrics, tracing, and DLQ or failure destination.
3. Inject duplicate events, timeouts, and downstream failures to validate retries and idempotency.
4. Create alarms for errors, throttles, duration, iterator age or queue age, and DLQ messages.
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